Electrical measuring-instrument



(No Mbdel.)

W. H. BRISTOL.

ELECTRICAL MEASURING INSTRUMENT.

No. 533,270. Patented Jan 29, 1895.

. (R in INVENTORI William H. Br'wc o\ ATTOR N EY WITNESSES:

Ag @Wa UNITED STATES PATENT OFFICE.

WVILLIAM H. BRISTOL, OF HOBOKEN, NEXV JERSEY.

ELECTRICAL MEASURING-INSTRUMENT.

SPECIFICATION forming part of Letters Patent No. 533,270, dated January29, 1895.

Application filed September 24, 1894. Serial No. 523,874- (No model.)

To all whom, it may concern.-

Be it known that 1, WILLIAM H. BRISTOL, a citizen of the United Statesof America, and a resident of Hoboken, in the county of Hudson and Stateof New Jersey, have invented certain new and useful Improvements inElectric Measuring-Instruments, of which the following is aspecification.

My invention has reference to electrical de vices of that characterespecially adapted for use in galvanometers, ampere -meters, andsimilarinstruments for indicating and recording an electric current, orthe Work done thereby.

It has forits objects to provideasensitiveinstrument, such as anampere-meter, in which the divisions of the scale are quite uniform andin which the vibrations of the moving armature, due to inertia, arereduced to a minimum,whereby the instrument is rendered practically deadbeat,and an accurate and easily read record produced. With theseobjectsin view,I construct the metallic armature in the form of a thin disk,making it as light as possible in all respects, so as to reduce themomentum acquired to a minimum, and provide a damping device offering aresistance to the movement of the armature toward and from theattracting coil, which prevents the indicating or recording arm frombeing carried to any appreciable extent beyond the positioncorresponding to the current in case of sudden fluctuations in thestrength of the same, and in general prevents undue vibration of thearmature. I also provide the armature With a core entering the coil orsolenoid and so arranged that it offers increased magnetic resistance tothe motion of the armature as it approaches the coil or solenoid andpermits the scale to be made quite uniform.

The nature of my said invention will best be understood when describedin connection with the accompanying drawings, in which Figure 1represents a Vertical section in the plane l1, Fig. 2, of anampere-meter embodying my invention. Fig. 2 is a vertical cross-sectionin the plane 2-2, Fig. 1. Fig.

3 is a sectional front elevation, part being broken away. Fig. 4 is aperspective detail Fig. 5 is a of the armature and its shaft.

cross-section of a bi-metallic armature drawn to a larger scale than thepreceding figures.

Similar letters of reference designate corresponding parts throughoutthe several views.

Referring to the drawings, the letter E designates a coil or solenoidsecured to the back of the casing, and A is a movable armature arrangedin line with the coil E.

The armature A is secured to a horizontal non-magnetic shaft Ct passingthrough the coil or solenoid E and having at opposite ends V- shapednotches b b. The notches rest on knife edges formed in flexible supportsJ J secured to a suitable bracket 0 affixed to the back of the casing.The coil or solenoid E has its terminals 6 6, connected to binding postsF F secured to the casing.

To an extension of the flexible support J is secured a pointer,recording arm, or like deviceI arranged adjacent to a scale or chart Sin the usual manner. In this instance I have shown a recording armattached to the support J and having a style bearing on a chart S, towhich latter a rotary motion is imparted by a suitable clock movement 0.

It will be readily seen that when the armature A moves toward the coilor solenoid E, the flexible support J is deflected about its point ofattachment and consequently the recording arm I, which practically formsa prolongation of said support, participates in said movement about thepoint of attachment of the support as acenter, and moves through agreatly increased arc, thereby permitting levers and similar multiplyingdevices to be dispensed with.

As before stated the main objects of my present invention are, first, toreduce to a minimum the vibrations due to the inertia of the armatureand, secondly, to obtain a uniform scale.

Relative to the vibrations I attain the end sought by making thearmature quite thin and light, preferably in the form of a disk abouttwo and one half inches in diameter and 0.005 inches thick. The disk ispreferably made bimetallic, say, of iron and brass, the iron being, asstated, very thin to reduce the error due to magnetic lag to a minimum,while the brass or other non-magnetic metal imparts strength andrigidity to the disk.

